This invention relates in general to imaging, and more specifically to migration imaging wherein a migration marking material is selectively moved through a softenable medium and the development of migration imaging members to effect the selective movement of the migration marking material through such a softenable medium, or to enhance the quality of such migration-type images.
Recently, a migration imaging system capable of producing high quality images of high density, continuous tone, and high resolution has been developed. Such migration imaging systems are disclosed in copending applications Ser. No. 837,780, and Ser. No. 837,591, both filed June 30, 1969. In a typical embodiment of the new migration imaging system an imaging member comprising a substrate, a layer of softenable material and electrically photosensitive marking material is latently imaged by electrically charging the member and exposing the charged member to a pattern of activating electromagnetic radiation, such as light. Where the photosensitive migration marking material was originally in the form of a fracturable layer at the upper surface of the softenable layer, particles of the migration marking material in the exposed areas of the imaging member migrate toward the substrate when the member is developed by decreasing the resistance of the softenable layer to migration of the marking material toward said substrate.
"Softenable" as used herein is intended to mean any material which can be rendered more permeable thereby enabling particles to migrate through its bulk. Conventionally, changing the permeability of such material or reducing its resistance to migration of migration marking material is accomplished by dissolving, melting, and softening, by methods, for example, such as contacting with heat, vapors, partial solvents, solvent vapors, solvents and combinations thereof, or by otherwise reducing the viscosity of the softenable material.
"Fracturable" layer or material as used herein, means any layer or material which is capable of breaking up during development, thereby permitting portions of said layer to migrate toward the substrate or to be otherwise removed. The fracturable layer may be particulate, semi-continuous, microscopically discontinuous or continuous in various embodiments of the migration imaging members of the present invention. Such fracturable layers of marking material are typically contiguous the surface of the softenable layer spaced apart from the substrate, and such fracturable layers may be near, at, coated onto, or slightly, partially or substantially embedded in the softenable layer in the various embodiments of the imaging members of the inventive system. "Contiguous" for the purpose of this invention is defined as in Webster's New Collegiate Dictionary, Second Edition 1960: "In actual contact; touching; also, near, though not in contact; adjoining," and is intended to generically describe the relationship of the fracturable layer of marking material in the softenable layer, vis-a-vis the surface of the softenable layer spaced apart from the substrate.
There are various other systems for forming such images, wherein non-photosensitive or photosensitivity inert, marking materials are arranged in the aforementioned fracturable layers, or dispersed throughout the softenable layer in a binder configuration, as described in the aforementioned copending applications, which also disclose a variety of methods which may be used to form latent images upon such migration imaging members.
Various means for developing the latent images in the novel migration imaging system may be used. These development methods include solvent wash-away; solvent vapor softening, heat softening, and combinations of these methods, as well as any other method which changes the resistance of the softenable material to the migration of particulate marking material through said softenable layer to allow imagewise migration of the particles toward the substrate. In the solvent wash-away development method, the migration marking material migrates in imagewise configuration toward the substrate through the softenable layer as it is softened and dissolved, leaving an image of migrated particles corresponding to the desired image pattern on the substrate, with the material of the softenable layer substantially completely washed away. In the heat or vapor softening developing modes, the softenable layer is softened to allow imagewise migration of marking material toward the substrate and the developed image member generally comprises the substrate having migrated marking particles near the softenable layer-substrate interface, with the softenable layer and unmigrated marking materials intact on the substrate in substantially their original condition.
Various methods and materials and combinations thereof have previously been used to fix unfixed migration images. For example, fixing methods and materials are disclosed in copending applications Ser. No. 590,959, filed Oct. 31, 1966, and Ser. No. 695,214, filed Jan. 2, 1968.
In new and growing areas of technology such as the migration imaging systems of the present invention, new methods, apparatus, compositions of matter, and articles of manufacture continue to be discovered for the application of the new technology in new modes. The present invention relates to a new and advantageous system for the development of latent images or partially developed images in such migration imaging systems.